Dislocation Tangles, Cell Structure and Long-Range Stresses in Deformed Metal Crystals

摘要

A method was developed for the detection and characterization of microcracks based on the anomalous transmission (AT) of X-rays. The method consists of localizing the lattice defects by employing a highly divergent incident X-ray beam and subsequently imaging the defect structure with a parallel incident beam to obtain a selected area topograph. The presence of the microcracks smaller than 50A in size has been disclosed in intrinsic germanium crystals by the destruction of AT in certain areas of the bent specimen when scanned by the divergent X-ray beam. Upon removal of the bending moment the AT in these areas was fully restored, thus indicating that the microcracks in germanium open and close on an atomic scale with the application and removal of the stress. It was possible to blunt the tip of the cracks by annealing and to show that the microcracks represent important dislocation sources when a small stress was applied at elevated temperatures. (Author)